High-contrast room-light-handleable black-and-white silver halide photographic elements are well known and widely used in graphic arts applications. The term "room-light-handleable" is intended to denote that the material can be exposed to a light level of 200 lux for several minutes without a significant loss in performance.
The silver halide emulsions utilized in high-contrast room-light-handleable photographic elements are slow speed emulsions, with the desired slow speed typically being achieved by the use of small grain sizes and by the doping of the silver halide grains with appropriate doping agents that control photographic speed. The incorporation of filter dyes in an overcoat layer of the photographic element to absorb unwanted light and decrease photographic speed is also a commonly employed technique.
Most commonly, the high-contrast room-light-handleable black-and-white silver halide photographic elements are ultraviolet-sensitive elements that are exposed by contact-exposure techniques. These photographic elements require a high degree of dimensional stability as well as a surface which is non-tacky and has a suitable degree of roughness to facilitate rapid vacuum draw-down during contact exposure.
An electrically-conductive layer comprised of electrically-conductive metal-containing particles dispersed in a film-forming polymer is advantageously incorporated in the aforesaid high-contrast room-light-handleable contact-exposed ultraviolet-sensitive photographic elements to provide process-surviving antistatic protection. However, such use of metal-containing particles can create an halation problem, i.e., a problem of image degradation resulting from unwanted reflections of light. It is believed that the halation problem results from the fact that the electrically-conductive layer forms two interfaces with significant index of refraction offsets, and therefore significant reflection of light during exposure. This "mirror-effect" causes unwanted halation with high-contrast room-light-handleable contact-exposed elements that do not contain an anti-halation underlayer. Increasing the concentration of metal-containing particles in the electrically-conductive layer beyond what is needed to obtain the desired level of electrical conductivity can serve to avoid this unwanted halation problem. This is apparently due to the action of the "excess" metal-containing particles in acting as an anti-halation agent. However, use of such high concentrations of metal-containing particles results in excessively high UV D.sub.min after processing, which creates problems in subsequent exposure steps.
The present invention is directed toward the objective of providing a high-contrast room-light-handleable contact-exposed ultraviolet-sensitive photographic element that combines effective antistatic protection with low UV D.sub.min and minimal halation.